PROJECT SUMMARY Excessive alcohol consumption has widespread personal and societal consequences, negatively affecting individual health while creating a significant economic and legal burden. Despite increasing efforts over the last few decades to identify genetic influences and neuroadaptations that are associated with the development of alcohol use disorders (AUDs), progress has been limited by the complexity of the underlying neuroanatomy. It is clear that the experimental resolution needs to be improved to the level of identifying adaptations in specific neural circuits that underlie dissociable behaviors related to AUD pathology. Thus, the goal of my research is to identify the neuroadaptations resulting from adolescent binge drinking that perpetuate heavy drinking and cognitive deficits in adulthood. I have focused my research on the prefrontal cortex (PFC), as this region continues to develop during adolescence and may be vulnerable to heavy alcohol consumption. For instance, PFC dysfunction is observed in binge drinkers and likely contributes to compulsive alcohol drinking and cognitive deficits observed in AUDs. In mice, I have found that binge drinking during adolescence disrupts performance on a PFC-dependent working memory task, increases alcohol consumption in adulthood, and significantly alters the intrinsic excitability of PFC pyramidal neurons. Discerning the mechanisms underlying these effects requires the use of tools capable of detecting physiological changes in specific neural circuits, as well as the ability to modulate their activity during behavioral analyses. In the mentored phase (K99) of this proposal, I will learn to use viral genetic strategies to visualize PFC projections affected by binge drinking and characterize the circuit-specific changes in excitability following adolescent binge drinking using ex vivo electrophysiology. Further, I will be trained to modulate PFC activity during behavior using chemogenetics, toward the goal of determining the specific role of these prefrontal pathways in binge-drinking and working memory. In the R00 phase, I will utilize a newly developed system for gaining permanent genetic access to neuronal ensembles that are active during defined behaviors (FosTRAP). In combination with the techniques learned in the mentored phase, I will use this technique to identify, characterize and modulate neuronal ensembles engaged in binge-like alcohol consumption. Taken together, the experiments in this proposal were designed to test the overarching hypothesis that adolescent binge drinking differentially affects the intrinsic excitability of medial PFC pyramidal neuron subpopulations and that these subpopulations play separate roles in binge alcohol consumption and working memory. The proposed experiments will integrate my previous training in behavioral pharmacology, immunohistochemistry and electrophysiology with new viral genetic strategies to identify and manipulate neural circuits. This training plan, in combination with guidance provided by my mentors, will greatly improve my ability to answer important research questions regarding the neurobiology of alcoholism while promoting my transition into an independent research scientist.